Jar stroke accelerator for pumpdown well tool

ABSTRACT

A jarring stroke accelerator for pumpdown well tool operation for reducing the effect of pumpdown operating fluid on the pumpdown locomotive pistons used with hydraulic jarring tools in pumpdown well operations wherein a liquid is used as the operating fluid. The expansible and contractable chamber provides a low-pressure chamber for movement of a pumpdown locomotive with respect to another tool in a well in which the locomotive is manipulated by liquid operating fluid. Variable capacity accelerators are provided, as are convertible accelerators which may be modified for use to apply strokes in opposite directions.

United States Patent Adkins 51 Feb. 15,1972

JAR STROKE ACCELERATOR FOR PUMPDOWN WELL TOOL Joel E. Adkins, Carrollton, Tex.

Assignee: Otis Engineering Corporation, Dallas, Tex.

Filed: Sept. 28, 1970 Appl. No.: 76,188

lnventor:

U.S.Cl .Q ..166/301, l66/153, 166/178, 175/296 Int. Cl .1321!) 23/00 Field of Search ..l75/296, 297; 166/301, 178, 166/153,155, 156

References Cited UNITED STATES PATENTS l/l956 Burns, Jr 175/297 2,801,078 7/1957 Meddens et al 175/297 Primary Examiner.lames A. Leppink Attorney-J5. Hastings Ackley [57] ABSTRACT 16 Claims, 15 Drawing Figures msmsarzs 15 m2 3. 642 O69 SHEET 2 OF 3 IN VENTOR.

PATENTEBFEH 15 I972 3. 642. 069

SHEET 3 OF 3 M1 5! F/G. 14 F/G. 15

INVENTOR.

ATTORNEY JAR STROKE ACCELERATOR FOR PUMPDOWN WELL TOOL This invention relates to new and useful improvements in well tools, and more particularly to jarring stroke accelerators for use in pumpdown tool well operations.

One object of the invention is to provide an accelerator device for use with hydraulic jarring tools for permitting relative movement of a pumpdown locomotive or piston assembly with respect to another tool in a column of liquid in a flow conductor.

Another object of the invention is to provide an accelerator device for use with a hydraulic jarring tool for permitting an increased speed of movement of the jarring tool by reducing the volume of liquid between two separate locomotive piston assemblies to permit one of the assemblies to move toward the other without disturbing the column of liquid used in circulating the tools into and out of the well flow conductor.

It is still another object of the invention to provide a pumpdown accelerator and jarring mechanism combination which is operable by pumpdown tool strings in through-the-flowline pumpdown well installation for imparting a substantial impact to tools in the well flow conductor for operating the same.

A particular object of the invention is to provide means for producing a chamber of reduced pressure in a pumpdown tool operating string for use in coaction with a hydraulic jarring mechanism for the purpose of permitting movement to actuate the jarring mechanism without causing movement of the entire column of liquid in the pumpdown system.

A further object of the invention is to provide a pumpdown accelerator mechanism which is operable to provide a chamber of reduced pressure in a column of liquid in a pumpdown well installation to permit sudden movement of the actuating tools of the pumpdown tool string without causing corresponding movement of the liquid column in the pumpdown system.

Another object of the invention is to provide a pumpdown accelerator operable for permitting movement of the tools in one direction and which may be adjusted to permit movement of the tools in the opposite direction in the flow conductor when desired.

Still another object of the invention is to provide a pumpdown accelerator device of the character described in which the volume of the chamber of reduced pressure may be varied to accommodate either a longer longitudinal movement or a higher speed longitudinal movement when desired.

A still further object of the invention is to provide a pumpdown accelerator which is simple in construction, economical to manufacture and operate and reliable and efficient in operation.

Still another object of the invention is to provide a pumpdown accelerator and jarring tool assembly which is operable to apply an impact stroke in the well flow conductor in either longitudinal direction thereof, as desired or selected.

Still another important object of the invention is to provide an improved method of actuating a pumpdown tool system to impart an impact of substantial force to a well tool in a pumpdown tool well installation with minimum movement of the circulating fluid of the system.

Additional objects and advantages of the invention will be readily apparent from the reading of the following description of a device constructed in accordance with the invention, and reference to the accompanying drawings thereof, wherein:

FIG. 1 is a schematic view of a well installation showing a portion of a well flow conductor having a pumpdown tool string therein with the accelerator and jarring mechanism of the invention arranged for applying an upward stroke to a well tool in place in the flow conductor;

FIG. 2 is an enlarged view, partly in elevation and partly in section, of the pumpdown accelerator used in FIG. 1;

FIG. 3 is an enlarged fragmentary vertical sectional view of one side of a piston for the mechanism of FIG. 2 showing a modified form of sealing element;

FIG. 4 is a view similar to FIG. 3 of a further modified form of sealing means on the piston;

FIG. 5 is an enlarged fragmentary sectional view showing a spring loaded one-way check valve in the cylinder of the accelerator body for cooperation with the piston of the accelerator to quickly produce a low pressure in the chamber of the accelerator;

FIG. 6 is a view similar to FIG. 2 of a modified form of the pumpdown accelerator showing the same in condition for use in combination with a jarring mechanism for applying a down stroke to well tools in the flowconductor;

FIG. 7 is a continuation of FIG. 6 showing the upper portion of the device;

FIG. 8 is a view, partly in elevation and partly in section, of a further modified form of the pumpdown accelerator showing a device convertible for use in either direction and for provided variable volumes;

FIG. 9 is a view similar to FIG. 8 of a still further modified form of the pumpdown accelerator;

FIG. 10 is a horizontal cross-sectional view taken on the line 10-10 ofFIG. 9;

FIG. 11 is a schematic view of a well flow conductor having a pumpdown tool string therein showing the string in position preparatory to striking an upward impact to a well tool in the conductor;

FIG. 12 is a view similar to FIG. 11 showing the pumpdown tool string striking the upward impact;

FIG. 13 is a view similar to FIG. 10 of a pumpdown tool string having a jarring device and accelerator mechanism therein position forstriking a downwardimpact to a well tool in the flow conductor;

FIG. 14 is a view of the pumpdown tool string of FIG. 12 immediately prior to activating the jarring device; and

FIG. 15 is a view similar to FIG. 12 showing the jarring device and accelerator activated to impact the downward impact to the well tool in the conductor.

In the drawings, FIG. 1, is shown a schematic illustration of a well flow conductor C having a well tool T therein having a fishing connection 10 at its upper end engaged by the dogs ll of a fishing tool F connected by means of a connector member 12 to an oil jar other hydraulic jarring device .I. The jarring device is connected by means of a connector 13 to a pumpdown tool locomotive piston assembly P-l, which is in turn connected by a connector I4 to a pumpdown accelerator A. The accelerator is connected at its other end by a connector 15 to a second pumpdown tool locomotive assembly P2.

Well fluids in the well flow conductor C are circulated in the usual manner through a U-tube flow pattern, the fluids in the conductor being in this case moving from bottom toward the top of the conductor to move the pumpdown locomotive assemblies P-1 and P-2 upwardly in the conductor in an effort to dislodge or free the well tool T from its position in the conductor. If it is impossible to move the well tool in the usual manner by means of the circulated pumpdown tool operating fluid in the system, the jarring device J and accelerator A may be utilized to deliver an impact of desired force to the fishing tool F to jar or drive the tool free of its stuck or lodged position in the flow conductor.

The well tool T may consist of a string of pumpdown tools including a plurality of locomotive assemblies such as the locomotive assemblies B-1 and B-2, or may comprise a flow control device or similar tool which has become lodged in the I flow conductor C so as not to be movably by the application of a pressure force resulting from the application of pressure to the column of circulating operating fluid in the system acting on the locomotive pistons B-1 and 3-2. A constant pressure force such as would be developed by the action of the operating fluid on the pistons does not produce an impact or jarring force applied to the lodged well tool T when a continuous pressure is applied to the operating fluid. If, however, it is attempted to apply sudden force by means of changes in direction of flow or pressure of the operating fluid to the pistons to move the same to apply sudden force to the lodged well tool T, the entire column of operating fluid in the U-tube system must be moved as a unit, and such a long column of liquid has a great inertia resisting sudden movement of the entire column to apply impact to the lodged well tool. Similarly, the jarring device J cannot be operated to produce a sufficiently great jarring impact by the movement of the column of liquids in the U-tube flow path, since the entire column of liquid must be moved as a unit to produce the movement of the jarring device and the inertia of the column resists any sudden movement of the jarring device which would produce the desired impact. Furthermore, the circulation of the fluids past the lodged well too] T in the flow conductor restricts the flow of the operating fluids past such well tools and further restricts the movement of the column of liquid in the U-tube system and increases the inertia or resistance to sudden movement of the column and so prevents the production of an impact to the jarring device. Also, the application of high pressure to the operating fluid could result in damage to the flow conductor itself or to the tools being operated in the system, as by rupturing or separating the flow conductor sections at the couplings or by destruction of the well tools or operating tools in the system.

It is for the purpose of producing a condition which will enable the jarring device to be operated safely, efficiently and with rapidity by the column of operating fluid in the system that the accelerator A of the invention is incorporated in the string of tools.

To actuate the jarring device J swiftly, the accelerator provides a means for permitting movement of the elements of the jarring device through their stroking movement with sufflcient rapidity to produce a desired impact force. This is accomplished by providing a chamber or region of substantially reduced pressure which is quickly collapsible or compressible by the liquid in the column of operating fluid between the column downstream of the locomotive assembly and the column upstream of the jar, which permits movement of the jar through its stroking action without substantial interference to such movement by the operating fluids. In other words, a substantial void is provided in the column of operating fluid between the downstream column and the upstream column which is sufficient to permit the locomotive piston which actuates the jarring device to move with rapidity through the length of stroke of the jarring device without requiring movement of the downstream operating fluid column.

The column of fluid acting to move the jarring device through its stroking movement is permitted to act on the accelerator to effect such movement of the jarring device through its jarring stroke as a result of the pressure of the operating fluid acting thereon against the void or region oflow pressure in the accelerator.

The accelerator A shown in FIG. 2 is designed for use in applying a longitudinal impact to the jarring device J in an upward direction or in the direction from the operating locomotive assembly piston P-l toward the locomotive piston assembly P-Z. The accelerator includes a cylindrical body having a bore 21 which is closed at one end by a closure head 22 having a counterbore 23 provided therein which communicates by means of a lateral port 24 with a threaded opening 25 extending to the exterior of the head. The port 24 is closed by means of a seal plug member 26 which is held in place by a set screw 27 threaded into the threaded bore 25 to provide a fluid tight closure for the lateral port 24. The head has a coupler socket 28 formed integral therewith having a bore 280 therein for receiving the connector member 14, whereby the accelerator is coupled in the pumpdown tool string as has been previously described. The coupler socket and connector 14 are substantially identical with those illustrated and described in the vpatent to John B. Fredd, US. Pat. No. 3,428,346, issued Feb. 18, 1969, by means of which the accelerator is connected to the locomotive piston assembly P] which is likewise of the general typedescribed in such patent.

A piston 30, which is connected to or carried by the lower end of an elongated piston rod 31, is slidable in the bore 21 of the cylinder 20, and a seal member 32, such as an O-ring, is disposed in an external annular groove 33 formed in the cylindrical external wall of the piston for sealing between the piston and the bore wall of the cylinder for purposes which will be hereinafter more fully described. The piston rod 31 extends upwardly through the bore 21 of the cylinder 20 and outwardly through a guide bushing 34 threaded into the upper end of the cylinder, and is connected at its upper projecting outer end to a coupler socket 35 threaded thereonto and secured in place thereon by means of a pin 36 extending through a transverse bore in the coupler socket and piston rod. The coupler socket has a bore or socket 35a which receives the connecting members 15 in the same manner as the coupler 28 receives the connector members 14 at the opposite end of the accelerator device. The guide bushing 34 is provided with a plurality of longitudinally extending slots 37 which are spaced circumferentially around the bore of the bushing to provide fluid passageways between the piston rod and the bushing for movement therethrough of the fluids which would otherwise be trapped in the bore 21 of the cylinder above the piston, so that the fluids may move easily and quickly into and out of the bore of the cylinder above the piston.

If desired, a spanner wrench opening or socket 34a may be provided in the flanged upper end of the bushing 34 for tightening the bushing in the cylinder.

It will be seen that movement of the piston 30 upwardly away from the head 22 of the cylinder 20 will produce a chamber or region of reduced pressure between the piston and thehead of the cylinder. Thus, if the accelerator is located in a column ofliquid fluid, the fluid of the column which is present in the bore 21 of the cylinder above the piston 30 will be displaced upwardly through the flow passages 37 and a substantial void or low-pressure region will be produced in the bore of the cylinder below the piston. The seal plug 26 held in place by the lock screw 27 effectively closes the lateral port 24 to prevent the liquids in the column from entering the bore 21 of the cylinder below the piston 30, whereby the region of reduced pressure or substantial void is produced in the chamber by the bore of the cylinder below the piston. Thus, when desired, the piston 30 may be moved quickly by the pressure of the fluids in the column of operating fluid acting thereon, from the upper position of the piston, downwardly in the cylinder to the lower position therein shown in FIG. 2, and so produce a rapid telescoping movement of the piston rod and of the cylinder with respect to each other, to permit or cause a rapid movement of the jarring device J through its jarring stroke to produce an impact of a desired force on the well tool T by means of the jar.

The action of the accelerator and jar is illustrated schematically in FIGS. 11 and 12, for the purposes of clarity and simplicity of explanation. As shown in FIG. 11, the accelerator A has been moved to the extended position in which the piston 30 is spaced from the cylinder head 22 to produce the void space in the bore 21 of the accelerator cylinder 20. With the tools in this position, further upward force applied to the upper locomotive piston assembly P-2 and the lower locomotive piston assembly P-l will move the piston 18 of the jarring device upwardly in the reduced lower portion 17a of the bore 17 in the cylinder 16 of the jarring device, and move the piston 18 upwardly out of such reduced lower portion into the enlarged upper portion 17 of the bore, where the piston may move rapidly through the oil or other fluid confined within the bore of the cylinder 16 of the jarring device. The piston rod 19 of the jarring device, being connected by means of the connector 13 to the lower locomotive piston assembly P-l will move rapidly with the lower locomotive piston P-l toward the upper locomotive piston P-2, such movement being possible because the accelerator piston 30 is movable toward the closure head 22 of the accelerator cylinder 20 by the pressure of the operating fluid acting on the cylinder in opposition to the relative void in the bore 21 of the accelerator cylinder between the piston and the head. The liquids in the space in the conductor C between the lower locomotive piston assembly P-1 and the upper locomotive piston assembly P-2 will enter the bore of the accelerator cylinder above the piston 30 during such movement, the flow passageways 37 permitting rapid transfer of the liquids from the exterior of the cylinder to the interior thereof as a result of the substantial differential between the pressure of the operating fluid or liquids and the substantial void within the bore of the accelerator cylinder below the piston 30.

The volume of the region within the accelerator chamber which is under reduced pressure, or which is a substantial void, must be sufficient to permit movement of the jarring device through its full stroke.

Thus, the accelerator provides means for actuating a jarring device J, of the oil jar type or similar delayed release stroking device, to effect a sudden movement to produce an impact of a desired value as a result of the action of the pressure of the operating fluid as opposed to the reduced pressure chamber or region within the accelerator.

A modified form of sealing assembly for thepiston of the accelerator is shown in FIG. 3, wherein a one-way seal structure of the type illustrated and described in the patent to Jack W. Tamplen, US. Pat. No. 3,227,462, issued Jan. 4, 1966, is disposed in the external annular groove 33 formed in the piston. The piston 30 having the groove 33 therein has an O- ring sealing element 320 and a ventilated backup ring 33a disposed between the O-ring and one of the sides of the annular groove in which the sealing assembly is located. The ventilated backup ring has one or more lateral flow courses 33b formed in the surface of the ring which abuts the sidewall of the groove nearest which the ring is disposed. The bypass flow passages 33b permit flow of fluid pressure from below the piston 30 past the O-ring and through the bypass passages into the bore 21 of the cylinder 20 above the piston, so that the piston may return quickly from the extended position to the fully telescoped position. However, as is set forth in the Tamplen patent, the O-ring 32a will abut the shoulder or sidewall of the annular groove opposite the ventilated backup ring to seal between the piston and the bore wall 21 of the cylinder when the piston is moved upwardly toward the extended position, to provide a substantial vacuum or void or volume or region of reduced pressure within the cylinder bore.

A further modified form of sealing assembly is shown in FIG. 4, wherein the piston 130 has an external annular groove 133 formed thereon in which a V-type packing ring 132 is supported between a pair of backup rings 133a and l33b. A split retaining ring 1336 is disposed in an annular locking recess 133d which is of smaller diameter than the groove 133 in which the packing or sealing member is positioned and confines the sealing assembly between the retaining ring 1336 and the shoulder 133e at the lower end of the groove 133. This seal assembly will also permit the piston to move quickly from the fully extended position toward the fully telescoped position for permitting any fluids within the bore 21 of the cylinder 20 to move past the V-shaped packing ring as the piston moves downwardly in the cylinder, but will seal upon upward movement to provide the desired void in the chamber when the piston is moved upwardly to the extended position of the piston rod, it being well known that the V-type packing rings will only seal in one direction, as was also the case of the form of the seal shown in FIG. 3.

To further assist in rapid return of the piston of the accelerator in the cylinder 20, the spring-pressed check valve shown in FIG. 5 may be mounted in the threaded opening 25 after the closure plug or sealing plug 26 and the retaining set screw 27 have been removed therefrom. The check valve functions for facilitating return of the piston 30 of the device shown in FIG. 2 from extended to collapsed or telescoped position of the piston rod without the necessity of changing the sealing assembly from that shown in FIG. 2 to provide a one-way seal rather than two-way seal shown therein.

The check valve includes a threaded body bushing 140 having a bore 141 which is restricted at its outer portion 142 to provide a shoulder 143 which supports a helical coil spring 144 in the bore 141 of the bushing. A ball closure valve member is biased into engagement with the beveled seat 146 formed at the outer end of the lateral port or aperture 24 in the closure head 22 of the cylinder 20. Thus, any fluids trapped in the bore 21 of the cylinder 20, or in the reduced bore 23 of the cylinder below the piston 30, will be permitted to flow outwardly through the lateral port 24 past the ball check valve 145 and through the bore 141and reduced bore 142 to the exterior of the cylinder to permit complete telescoping of the piston and piston rod in the bore of the cylinder of the accelerator. This check valve is designed for use 'with the O-ring of FIG. 2, which will seal in both directions, but may also be used in combination with the other-type seals to provide an assured evacuation or expulsion of fluids from within the bore of the cylinder 20 of the accelerator.

For movement of the jarring device in an opposite direction longitudinally of the string of pumpdown tools, the accelerator A-2 of FIG. 6 is provided. This form of the acceleratoris also operable in either direction longitudinally of the string of tools by proper positioning of the closure seal plug and retaining screw in the lateral apertures in the closed cylinder head 22, and in the guide bushing 134 at the upper end of the cylinder 20 of the accelerator. The cylinder 20 is identical to that of the form of the accelerator shown in FIG. 2. The bushing 134 differs in that the upper flange portion 134a of the bushing is elongated and provided with a lateral aperture 44 communicating with the longitudinal flow course 137 in the bore of the bushing and with an enlarged threaded opening 45. A closure seal plug 46 is held in closing sealing engagement with the inner end of the threaded bore 45 by a retaining screw 47 for closing the lateral port 44, in the same manner as the port 24 was closed in the accelerator of FIG. 2, to prevent passage of fluid through the lateral port. In addition, an external annular groove 48 is formed in the outer surface of the bushing below the upper flange portion 134a and an O-ring 49 is mounted therein for sealing between the bushing and the bore wall of the cylinder 20, and an internal annular groove 50. is formed in the reduced bore 137a of the upper portion of the bushing and an O-ring 51 is disposed in the groove and seals between the bushing and the piston rod 31. A spanner wrench aperture 134b may be formed in the flange portion of the bushing for tightening the bushing into the threaded upper end of the bore 21 of the cylinder in the same manner as in the form of FIG. 2.

In this form of the accelerator device, the piston is normally in the upper position with the piston rod 31 in extended position projecting from the cylinder 20. The O-ring 32 in the an nular groove 33 in the cylinder 30 seals between the piston and the cylinder wall and, as the piston is moved downwardly in the bore of the cylinder, a region of reduced pressure or a void is formed in the bore of the cylinder above the piston 30 and below the bushing 134. The O-ring seal member 49 and the O-ring seal member 51 act with the closure seal plug 46 to close the upper portion of the chamber defined by the bushing against admission of fluids into the bore of the cylinder as the piston moves downwardly. Thus, when the piston is moved downwardly a void or region of low pressure is produced in the bore of the cylinder above the piston, and the piston may move rapidly upwardly in the cylinder when the pressure of the operating fluid is applied thereto cause actuation of the jarring device .I in a downward direction in the well string.

As is shown in FIGS. l3, l4 and 15, the jarring device J-lis designed for downward actuating movement of the piston and rod of the jarring device with respect to the cylinder in which the piston is disposed to produce a downward stroke or impact upon such downward longitudinal telescoping movement of piston and the rod with respect to the cylinder. This action produces a downward jarring impact upon the well tool T with which the tool string is connected by means of the fishing tool F and the dogs 11 and the fishing neck 10. In operation of the tool string in which the convertible accelerator device A-2 of FIG. 6 is connected the string is assembled in the condition illustrated in FIG. 13, wherein the fishing tool F is connected by the dogs 11 to the fishing neck 10 of the lodged well tool T.

The couplers 12 connect the fishing tool F to the jarring deviceJ-l at one end, while the couplers 13 connect the other end of the jarring device with the accelerator device A-2, which is in turn connected by the couplers 14 to a locomotive piston assembly P-l.

Since the chamber in the cylinder 20 of the accelerator device A-2 between the piston andthe closure and guide bushing 134 is maintained under substantially atmospheric pressure, and is sealed off by the O-ring 32 of the piston, the O-rings 49 and 51 in the bushing, and the closure plug or seal plug 46 in the lateral aperture or opening 45, the accelerator piston will be held or maintained in the upper position in which the piston rod is extended. Also, the jarring device 1-] is held in the position in which the piston 118 is in the reduced portion 117a of the bore 117 of the cylinder 116 of the jarring device with the piston rod 1 19 is held in an extended position. The enlarged portion of the bore 117 of the jar cylinder 120 is closed at its lower end, and oil or other fluid is confined within the cylinder to retain the piston in the reduced portion of the bore until sufficient force is applied thereto to move it out of the bore into the enlarged poriion 117 of the bore through which the piston may move with greater speed to deliver an impact or jarring stroke in the same manner as the jar J of the form first described.

With the tool string in the position shown in FIG. 13, the fluid pressure of the operating fluid in the U-tube flow conductor C of the well system moves the locomotive piston P-l downwardly toward the well tool T which is lodged in place in the conductor C and which is to be dislodged. The pistonv 30 of the accelerator moves downwardly in the bore 21 of the cylinder 20 of the accelerator A-2, and the piston rod 31 telescopes into the bore of the cylinder to the fully telescoped position shown in FIG. 14. Further force applied by means of the locomotive piston P] then acts through the accelerator A-2 upon'the piston rod 119 of the jarring device J-l to force the same downwardly and move the piston 118 of the jarring device downwardly out of the reduced upper portion 117a of the bore 117 of the cylinder 116 of the jarring device and into the enlarged bore 117, where the piston may move rapidly toward the closed lower end of the bore for the jarring stroke against the closed end of the cylinder, and through the fishing tool F to the lodged well tool T.

The rapid movement of the jarring piston and piston rod after the piston has been moved out of the reduced portion 117a of the bore ofthe cylinder 116 of the jarring device J-l is permitted by virtue of the region of reduced pressure in the bore 21 of the accelerator piston 20 between the piston 30 and the bushing 134 at the upper end of the cylinder, so that the cylinder 20 of the accelerator A-2 may move downwardly rapidly with respect to the piston and piston rod toward the position shown in FIG. to permit the piston 118 and the piston rod 119 of the jarring device J-l to move downwardly to the telescoped position to engage the lower closed end of the jar cylinder 116 to deliver the jarring stroke or impact. Any fluid trapped between the locomotive piston P-1 and the well tool T will not materially affect the movement of the jar and accelerator toward the well tool, since the void region or region of low pressure within the accelerator cylinder permits longitudinal movement of the cylinder of the accelerator with respect to the accelerator piston and rod to the extended position shown in H6. 15. Operating fluid within the conductor C will enter through the lateral openings 25 and the port 24 into the bore 21 of the cylinder of the accelerator device A-2 as the piston is moved upwardly in the cylinder to the extended position shown. The accelerator thus acts in the same manner as the form first described, but in a difierent direction, to permit a jarring impact of the jarring device in a downward direction rather than the upward direction shown in FIGS. 11 and 12.

All advantages of the accelerator first described are present in this form of the accelerator. In addition, however, this accelerator is convertible from a condition in which it is used for imparting the downward stroke just described, to a condition in which it is usable to impart an upward stroke in the same manner as the accelerator of FIG. 2. Such conversion is accomplished by removing the retaining screw 47 and seal plug 46 from the threaded opening 45 in the bushing 134, and placing the seal plug 46 in the opening 25 in the lower closed head of the cylinder and securing the plug in sealing position therein by means of the retaining screw 47 to close the lateral aperture 24 in the opening 25 against fluid movement therethrough. In this condition, the lateral aperture 44 and the threaded opening 45 are open to permit fluid to enter therethrough into the flow passages 137 and into the bore 21 of the cylinder 20 above the piston 30 and the void or region of reduced pressure would be formed in the bore of the cylinder between the piston and the head 22.

In this event, the accelerator A-2 would function in the same manner as the accelerator A shown in FIG. 2 and produce the same results.

If desired, of course, the apertures 24 and 44 may be enlarged to provide a larger flow passage into and out of the bore of the cylinder, or a plurality of such apertures and closure seal plugs and retaining screws may be provided to secure the desired volume of flow into and out of the cylinder.

A further modified form of accelerator A-3 is shown in FIG. 8. This accelerator is also convertible to provide for up or down strokes, and to provide a variable volume of displacement or movement for an increased jarring action when desired. The cylinder body 220 has a bore 221 which is closed at its lower end by a closure head 222 having a counterbore 223 formed axially therein, which communicates by means of Y a lateral port 224 with a threaded opening 225 extending to the exterior of the head. The port 224 is closed by means of a seal plug 226 which is held in place by a retaining screw 227 threaded into the bore 225 to provide a fluid tight closure for the lateral port 224. The head has a coupler socket 228 formed integral therewith with a bore or socket 228a therein for receiving the connecting members 14, whereby the accelerator is connecting in the pumpdown tool string in the same manner as the forms previously described.

A guide bushing 234 is threaded onto the upper end of the cylinder body 220, and an O-ring 234a disposed in an annular groove in the bushing seals between the bushing and body to prevent fluid leakage therebetween. The guide bushing is provided with enlarged portion 237 in the lower portion of its bore 2370 which communicates with a lateral port 244 and a lateral threaded opening 245 which provides a flow passage from the bore 221 of the cylinder body to the exterior thereof when the flow port 244 and threaded opening 245 are open, so that fluids may easily enter into and flow out of the bore of the cylinder. The reduced upper portion of the bore 237a of the bushing provides a guide surface for a cylindrical tubular piston rod or plunger 260, and an internal annular groove 250 formed in such reduced bore receives an O-ring seal member 251, which seals against the exterior of said tubular piston rod or plunger. The tubular plunger is slidable in the guide surface 237a between extended and telescoped positions in the bore of the cylinder body 220.

A piston 262 is threaded on the lower portion of the tubular piston rod or shaft 260 and is held in place thereon by a pin 2620 extending through aligned radially extending apertures in the piston and the shaft. An O-ring 2 62!) positioned in an internal annular groove in the upper portion of the bore 262a of the piston seals between the piston and the rod, and an external annular groove 263 formed in the midportion of the piston receives an O-ring seal member 264 which seals between the piston 262 and the wall of the bore 221 of the cylinder during movement of the piston and shaft longitudinally of the cylinder body, as will be hereinafter explained. The upper end of the tubular shaft or rod is provided with'an enlarged head 265 having a downwardly facing shoulder 266 which is adapted to engage the upper end of the bushing 234 when the shaft 260 and piston 262 are telescoped into the cylinder 220. The head 265 has a bore 267 therein communicating with the bore 261 of the tubular shaft 260, and a reduced bore at its upper end providing a guide surface 268 in which an internal annular groove 269 is formed for receiving an O-ring seal member 270 for sealing between the head 265 and a piston rod 231 having a piston 230 at its lower end. This piston 230 has an external annular groove 233 in which an O-ring seal 232 is disposed for sealing between the piston 230 and the wall of the bore 261 of the tubular shaft 260. The upper end of the piston rod 231 extends outwardly through the guide bore 268 and is threaded at its upper end into a counter bore 235b in the lower end of a coupler socket member 235 which has its lower external portion reduced at 235b to enter an enlarged bore 265a in the bushing 265. The piston rod 231 is pinned to the coupler socket member by a transverse retaining pin 280 extending through aligned radial apertures in the bushing 265, in the shank 2351; of the coupler socket 235, and in the upper end of the piston rod 231.

The coupler socket 235 has a bore 235a which is adapted to receive the connector members or coupler in the same manner as the same were received for connecting the device in the operating string in the form previously described.

In this form of the accelerator, the tubular shaft 260 having the piston 262 thereon is normally pinned by means of the connector pin 280 to the piston rod 231 having the piston 230 thereon, so that the two pistons move simultaneously as a unit in the bore 221 of the cylinder body 220, and, when the lower port 224 is closed by the closure plug 226 and the two pistons are moved upwardly in the bore 221 of the cylinder body, a vacuum or region of reduced pressure is formed in the bore of the cylinder body between the pistons and the closure plug 226 in the head 222, the same manner as the form of FIG. 2. This permits the application of a downward jarring stroke upon telescoping movement of the pistons in the cylinder body.

If a longer jarring stroke is desired, the connecting pin 280 may be removed to permit the piston rod 231 and the piston 230 thereon to slide in the bore 261 of the tubular shaft 260 so that the rod 231 is extended beyond the head 265 at the upper end of the tubular shaft 260. Such movement of the piston 230 and the rod 231 provides an increased volume of reduced pressure within the bore 261 of the tubular shaft 260 which is added to the volume within the bore 221 of the cylinder body 220 when the elements are in the extended position. This larger volume permits a longer stroke of the jarring device than is possible when the piston rod 231 is connected to the tubular shaft 260 by the pin 280.

Also, when the piston rod is connected to the tubular shaft 260 by the pin 280, the lateral port 244 may be closed by a closure plug and retaining screw with tubular shaft 260 in an extended position, similar to the device of FIG. 6, whereupon downward telescoping movement of the piston 262 and piston 230 simultaneously in the bore 221 of the cylinder body 220 will produce an area of lower pressure within the cylinder body 221 above the piston 262 and below the O-ring seal 251 in the guide bushing 234. Such movement of the connected pistons 262 and 230 in the bore 221 provides for an upward jarring stroke in the same manner as was accomplished by means of the device in FIG. 6, when the lower port 224 is opened by removing the closure plug 226 and retaining screw 227 to permit flow of fluids into the bore 221 of the cylinder body below the two pistons.

Similarly, the piston rod 231 may be disconnected from the head 265 and the tubular shaft 260 by removing the pin 280, and the lateral port 284 closed by a closure plug and retaining screw inserted in the threaded bore 285 to close the plug port 284, in which event the piston rod 231 may be moved to an extended position and the tubular shaft 260 may be moved to an extended position before the ports 284 and 244 are closed by the closure plugs so that telescoping movement of the piston 230 in the bore 261 of the tubular shaft 260 and further telescoping movement of the piston 262 in the bore 221 of the tubular body cylinder body will produce regions of reduced pressure or void in the bore 261 of the tubular shaft above the piston 230 and in the bore 221 of the cylinder body above the piston 262, which permits an elongated movement of the jarring device connected to the accelerator due to the increased volume of the region of reduced pressure so provided.

It will be seen, therefore, that this form of the accelerator provides for a variable volume of the region of reduced pressure or void in the accelerator, as desired; and, that the accelerator is convertible to permit upward or downward longitudinal jarring movement of the jarring device.

Another modified form of the accelerator is shown in FIGS. 9 and 10, wherein the accelerator A-4 also provides a variable volume or region of reduced pressure or void in the bores of the elements of the accelerator, but wherein the device is adapted for jarring movement in only one direction.

In this form of the device, the accelerator A-4 has a cylinder body 320 with a bore 321 having a plurality of circumferentially spaced radially inwardly extending guide ribs 337 in the upper portion of the bore of the cylinder body for guiding the elongate tubular piston shaft 360 in its longitudinal telescoping movement in the cylinder. The cylinder body 320 is threaded at its lower end into the enlarged threaded counter bore 322a of a closure head 322, and an O-ring seal 325 is disposed in an internal annular groove 326 formed in the cylinder for sealing between the cylinder and the bore wall of the enlarged counter bore 3220 of the closure member. The lower end of the closure member is formed with a coupler socket member 228 having a socket or bore 328a for receiving connector members 14 in the same manner as the forms of the accelerator previously described for connecting the accelerator in the string of operating tools. An elongate rod 331 has an enlarged lower end 330 which is threaded into a threaded reduced axial bore 327 in the closure member 322, and a seal ring 329 is disposed in an annular groove 330 in the reduced bore 327 above the threads for sealing between the rod and the closure head 322. The rod 331 extends upwardly in the bore 361 of the tubular shaft 360 to a point adjacent the upper end of the cylinder body 330. An internal annular groove 333 in the bore 361 of the piston 362 on the lower end of the tubular shaft 360 receives an O-ring seal member 332 which seals between the piston 362 and the exterior of the rod 331. The

piston 332 has an external annular groove 363 formed therein which receives an O-ring seal member 364 for sealing between the piston and the wall of the bore 321 of the cylinder body 320. The upper end of the tubular shaft 360 is threaded into the enlarged counter bore 365a in an upper coupler socket member 335 and is secured thereto by means of a set screw 336. The coupler member 335 has a socket or bore 33511 for receiving connector members 15 for connecting the accelerator in the tool string in the same manner as the forms previously described.

A closure bushing or plug 350 is threaded into the internally threaded upper end of the bore 361 of the tubular shaft 360 to removably close the same. The upper coupler socket member 335 has an axial reduced bore 357 which communicates with the counterbore of the socket member and the bore of the tubular shaft 360 above the plug 350.

In this form of the device, a variable volume is provided by removing the O-ring seal member 332 from the groove 333, in which event the entire area of the region in the bore 361 of the tubular shaft 360 below the plug 350 and the area in the bore 321 of the cylinder body 320 below the seal ring 364 on the piston 362 will provide an area of reduced pressure or void.

By removing the seal ring 364 from the groove 363, with the seal ring 332 in place, the area or region of reduced pressure is confined to that within the bore 361 of the tubular shaft 360 between the O-ring seal 332 and the plug 350.

When both the O-ring 332 and the O-ring 360 are in place, and the plug 350 is removed, the entire area beneath the piston 362 in the bore 321 of the cylinder body 320 is converted to an area or region of reduced pressure or void.

It will thus be seen that the volume of the region of reduced pressure or void may be varied by selectively removing one of the O-ring seals and by removing the plug 350 as has been described to provide varied volumes of void or regions of reduced pressure and so permit variations in the rapid actuation of the accelerator and the jarring device connected therewith in the tool spring. This device is adapted for accelerating a movementonly in the direction of telescoping movement of the piston 362 in the bore 321 of the cylinder body 320, and so a jarring stroke can only be effected in a down direction in the device as shown in FIG. 9, although it is possible to connect the device in the string of tools in the reverse position to provide for stroking movement of the jarring device in the opposite direction. The smaller volume region of reduced pressure is usable where the device is used in an area of higher fluid pressure'in the well U-tube flow system, while the larger volume of the region of reduced pressure is utilized where a lower fluid pressure area exists in the column of operating fluid. This provides for control over actuation of the jarring device in the well to prevent destruction of the tools or damage to the well conductor or well tools by an excessive jarring stroke.

Other features of the accelerators of the forms previously described are found in the device of this form.

The foregoing description of the invention is explanatory only, and changes in the details of the constructions illustrated may be made by those skilled in the art, within the scope of the appended claims, without departing from the spirit of the invention.

What is claimed and desired to be secured by Letters Patent l. A jarring stroke accelerator for pumpdown well tools including: a cylinder member; a piston movable longitudinally in said cylinder member; a piston rod connected with said piston and extending outwardly from said cylinder longitudinally beyond one end thereof; means at the other end of the said cylinder and at said projecting end of said piston rod for connecting the same to a string of pumpdown well tools including a jarring device; means sealing between the piston and the cylinder bore wall; said piston and rod when movable longitudinally of said cylinder producing a region of reduced pressure in said cylinder to permit said cylinder and piston to move quickly relative to each other in the direction ofsuch region of reduced pressure to permit operation ofajarring device by the pumpdown well tools.

2. A jarring stroke accelerator for use in a string of pump down tools comprising at least one pumpdown locomotive and a jarring device for operation in a well by operating fluid movement of said pumpdown well tool string including: a cylinder; a piston movable in the cylinder; a piston rod connected with the piston and projecting from the cylinder; means for connecting the projecting end of the rod to the pumpdown well tool string adjacent one of said pumpdown locomotive and said jarring device; means for connecting the cylinder of the accelerator to the pumpdown well tool string adjacent the other of the pumpdown locomotive and the jarring device in said pumpdown tool string; means for moving the piston and cylinder longitudinally in one direction relative to each other to produce a region of reduced pressure in the cylinder between the piston and the cylinder and between the pumpdown locomotive and the jarring device connected to the accelerator; said piston and cylinder of the accelerator being movable longitudinally relative to each other in an op posite direction to eliminate the region of reduced pressure within the accelerator cylinder to produce a rapid movement of the jarring device connected with the accelerator without disturbing the column of operating fluids in the system. 3. A device of the character set forth in claim 2 wherein the accelerator piston and cylinder are movable longitudinally in one direction from telescoped to extended position to create a region of reduced pressure in the cylinder between the piston and the cylinder; and the piston and cylinder are movable longitudinally in the opposite direction with respect to each other to collapse the region of reduced pressure to produce a sudden movement of the pumpdown tools connected with the accelerator by operating fluid movement.

4. An accelerator of the character set forth in claim 2 wherein the piston and cylinder are movable longitudinally from extended to telescoped position to produce a region of reduced pressure in the cylinder between the piston and the cylinder; and said piston and cylinder are movable longitudinally from telescoped to extended position to collapse said region of reduced pressure to produce sudden .movement of the pumpdown tools connected with the accelerator by movement of the operating fluid in the well.

5. For use in a pumpdown well installation having a U-tube flow path with a circulating operating fluid contained in said flow path, a string of pumpdown well tools in said flow path operable therein by movement by the fluid in the U-tube flow path including: a jarring device of a delayed action quick release type; and a jarring stroke accelerator for the jarring device comprising: a cylinder member having a bore; a piston movable longitudinally in the bore of said cylinder member; a piston rod connected with said piston and extending outwardly from said cylinder member longitudinally beyond one end thereof; means at the other end of the said cylinder member and at said projecting end of said piston rod for connecting the same to said string of pumpdown well tools adjacent said jarring device; means sealing between the piston and the cylinder bore wall; said piston and rod when movable longitudinally of said cylinder producing a region of reduced pressure in said cylinder bore to permit said cylinder and piston to move quickly relative to each other in the direction of such region of reduced pressure to permit operation of said jarring device by the movement of the circulating operating fluid acting on said pumpdown well tool string.

6. A pumpdown well tool string including: pumpdown locomotive means; a jarring stroke accelerator connected at one end with said'pumpdown locomotive means; a jarring device connected with the other end of said jarring stroke accelerator; and a well tool connected with said jarring device for actuation thereby, said accelerator comprising: a cylinder member having a longitudinal bore; a piston movable longitu dinally in the bore of said cylinder member; a piston rod connected with said piston and extending outwardly from said cylinder member longitudinally beyondone end thereof; means sealing between the piston and the cylinder member bore wall; said piston and rod when movable longitudinally of said cylinder member bore producing a region of reduced pressure in said cylinder member bore to permit said cylinder member and piston to move quickly relative to each other in the direction of such region of reduced pressure to permit operation of said jarring device by movement of the pumpdown locomotive means to actuate the well tool connected to the jarring device.

7. A method of accelerating the jarring stroke of a jarring device in a pumpdown well tool string operable by movement of circulating pumpdown fluid in a pumpdown well installation, which includes: creating a region of reduced pressure in the pumpdown fluid adjacent the pumpdown tools by moving one of the pumpdown tools by circulation of the pumpdown fluid in the pumpdown system to create said region of reduced pressure therein; actuating a jarring device in the string of pumpdown tools by the movement of the operating fluid to move said one pumpdown tool in a direction collapsing the region of reduced pressure to provide a sudden movement of the jarring device by the operating fluid.

8. A jarring stroke accelerator of the character set forth in claim 1 which includes: inlet opening means into said cylinder member adjacent each end thereof; means in one of said inlet opening means for closing said opening means against passage of fluid pressure whereby movement of the piston in the cylinder member produces said region of reduced pressure therein.

9. A jarring stroke accelerator of the character set forth in claim 1 wherein sealing means is provided between the end of the cylinder and the projecting piston rod for sealing therebetween; inlet opening means into said cylinder adjacent each end thereof; means in one of said inlet opening means for closing the same against passage of fluid pressure whereby movement of the piston in the cylinder member produces said region of reduced pressure therein; said closure means being selectively secured in a selected one of said inlet opening means to provide said region of reduced pressure on a selected side of said piston in said cylinder member.

10. A jarring stroke accelerator of the character set forth in claim 1 wherein: said piston and rod comprise a plurality of members, one telescoped within the other; means is provided for securing said plurality of members together for movement as a unit, said securing means being releasable to permit independent movement of said members relative to each other to provide an increased stroke and an increased region of reduced pressure in the cylinder member.

11. A jarring stroke accelerator of the character set forth in claim wherein: one of said plurality of members comprises a piston and a tubular stem movable in the cylinder member; sealing means is provided on said piston sealing between the piston and cylinder member; second sealing means is provided between said tubular stem and said cylinder member at one end of said cylinder member for sealing therebetween; a second piston and rod member is movable in the bore of said tubular stem with one end of said rod projecting from the bore of the stem, means sealing between said second piston and said tubular stern; and means for sealing between said rod and said tubular stem at the end of said stem opposite the piston thereon.

[2. A jarring stroke accelerator of the character set forth in claim 1 wherein said rod comprises a tubular stem having a piston thereon; a stationary rod is disposed in the tubular stem and is secured to one end of the cylinder member and extends to the opposite end thereof and is disposed to telescope into and out of said tubular stem; sealing means is provided for sealing between said piston and said cylinder and second sealing means is provided for sealing between said piston and said stationary rod; and means is provided for removably closing the bore of said tubular stem at the end thereof opposite the piston thereon.

13. A method of the character set forth in claim 7 including: the additional step of further moving the pumpdown well tool string by movement of the operating fluid in said installation after said jarring device has been actuated.

14. A method of accelerating the jarring stroke of a jarring device connected in a string of pumpdown well tools having a pumpdown locomotive therein operable by movement of circulating pumpdown fluid in a U-tube pumpdown well installation which includes: positioning a jarring stroke accelerator in the pumpdown tool string adjacent the locomotive and the jarring device connected in said string; moving said string of tools into said well installation U-tube by circulating pumpdown fluid to move said locomotive; creating a region of reduced pressure in the accelerator by circulating pumpdown fluid in the system to actuate said accelerator to produce said region of reduced pressure; applying force to said jarring device by means of the pumpdown fluid to release the jarring device for actuation; actuating said jarring device by moving the locomotive by means of the operating fluid in a direction to collapse the region of reduced pressure in the accelerator to provide sudden jarring movement of the jarring device.

15. A jarring stroke accelerator of the character set forth in claim 1 wherein the sealing means provided sealing between the piston and the bore wall of the cylinder member comprises a one-way seal on said piston.

16 A jarring stroke accelerator of the character set forth in claim 8 wherein the means in the inlet opening means of said cylinder member for closing the said opening means comprises a one-way check valve by preventing flow of fluids through the inlet opening means into the cylinder member bore. 

1. A jarring stroke accelerator for pumpdown well tools including: a cylinder member; a piston movable longitudinally in said cylinder member; a piston rod connected with said piston and extending outwardly from said cylinder longitudinally beyond one end thereof; means at the other end of the said cylinder and at said projecting end of said piston rod for connecting the same to a string of pumpdown well tools including a jarring device; means sealing between the piston and the cylinder bore wall; said piston and rod when movable longitudinally of said cylinder producing a region of reduced pressure in said cylinder to permit said cylinder and piston to move quickly relative to each other in the direction of such region of reduced pressure to permit operation of a jarring device by the pumpdown well tools.
 2. A jarring stroke accelerator for use in a string of pump down tools comprising at least one pumpdown locomotive and a jarring device for operation in a well by operating fluid movement of said pumpdown well tool string including: a cylinder; a piston movable in the cylinder; a piston rod connected with the piston and projecting from the cylinder; means for connecting the projecting end of the rod to the pumpdown well tool string adjacent one of said pumpdown locomotive and said jarring device; means for connecting the cylinder of the accelerator to the pumpdown well tool string adjacent the other of the pumpdown locomotive and the jarring device in said pumpdown tool string; means for moving the piston and cylinder longitudinally in one direction relative to each other to produce a region of reduced pressure in the cylinder between the piston and the cylinder and between the pumpdown locomotive and the jarring device connected to the accelerator; said piston and cylinder of the accelerator being movable longitudinally relative to each other in an opposite direction to eliminate the region of reduced pressure within the accelerator cylinder to produce a rapid movement of the jarring device connected with the accelerator without disturbing the column of operating fluids in the system.
 3. A device of the character set forth in claim 2 wherein the accelerator piston and cylinder are movable longitudinally in one direction from telescoped to extended position to create a region of reduced pressure in the cylinder between the piston and the cylinder; and the piston and cylinder are movable longitudinally in the opposite direction with respect to each other to collapse the region of reduced pressure to produce a sudden movement of the pumpdown tools connected with the accelerator by operating fluid movement.
 4. An accelerator of the character set forth in claim 2 wherein the piston and cylinder are movable longitudinally from extended to telescoped position to produce a region of reduced pressure in the cylinder between the piston and the cylinder; and said piston and cylinder are movable longitudinally from telescoped to extended position to collapse said region of reduced pressure to produce sudden movement of the pumpdown tools connected with the accelerator by movement of the operating fluid in the well.
 5. For use in a pumpdown well installation having a U-tube flow path with a circulating operating fluid contained in said flow path, a string of pumpdown well tools in said flow path operable therein by movement by the fluid in the U-tube flow path including: a jarring device of a delayed action quick release type; and a jarring stroke accelerator for the jarring device comprising: a cylinder member having a bore; a piston movable longitudinally in the bore of said cylinder member; a piston rod connected with said piston and extending outwardly from said cylinder member longitudinally beyond one end thereof; means at the other end of the said cylinder member and at said projecting end of said piston rod for connecting the same to said string of pumpdown well tools adjacent said jarring device; means sealing between the piston and the cylinder bore wall; said piston and rod when movable longitudinally of said cylinder producing a region of reduced pressure in said cylinder bore to permit said cylinder and piston to move quickly relative to each other in the direction of such region of reduced pressure to permit operation of said jarring device by the movement of the circulating operating fluid acting on said pumpdown well tool string.
 6. A pumpdown well tool string including: pumpdown locomotive means; a jarring stroke accelerator connected at one end with said pumpdown locomotive means; a jarring device connected with the other end of said jarring stroke accelerator; and a well tool connected with said jarring device for actuation thereby, said accelerator comprising: a cylinder member having a longitudinal bore; a piston movable longitudinally in the bore of said cylinder member; a piston rod connected with said piston and extending outwardly from said cylinder member longitudinally beyond one end thereof; means sealing between the piston and the cylinder member bore wall; said piston and rod when movable longitudinally of said cylinder member bore producing a region of reduced pressure in said cylinder member bore to permit said cylinder member and piston to move quickly relative to each other in the direction of such region of reduced pressure to permit operation of said jarring device by movement of the pumpdown locomotive means to actuate the well tool connected to the jarring device.
 7. A method of accelerating the jarring stroke of a jarring device in a pumpdown well tool string operable by movement of circulating pumpdown fluid in a pumpdown well installation, which includes: creating a region of reduced pressure in the pumpdown fluid adjacent the pumpdown tools by moving one of the pumpdown tools by circulation of the pumpdown fluid in the pumpdown system to create said region of reduced pressure therein; actuating a jarring device in the string of pumpdown tools by the movement of the operating fluid to move said one pumpdown tool in a direction collapsing the region of reduced pressure to provide a sudden movement of the jarring device by the operating fluid.
 8. A jarring stroke accelerator of the character set forth in claim 1 which includes: inlet opening means into said cylinder member adjaceNt each end thereof; means in one of said inlet opening means for closing said opening means against passage of fluid pressure whereby movement of the piston in the cylinder member produces said region of reduced pressure therein.
 9. A jarring stroke accelerator of the character set forth in claim 1 wherein sealing means is provided between the end of the cylinder and the projecting piston rod for sealing therebetween; inlet opening means into said cylinder adjacent each end thereof; means in one of said inlet opening means for closing the same against passage of fluid pressure whereby movement of the piston in the cylinder member produces said region of reduced pressure therein; said closure means being selectively secured in a selected one of said inlet opening means to provide said region of reduced pressure on a selected side of said piston in said cylinder member.
 10. A jarring stroke accelerator of the character set forth in claim 1 wherein: said piston and rod comprise a plurality of members, one telescoped within the other; means is provided for securing said plurality of members together for movement as a unit, said securing means being releasable to permit independent movement of said members relative to each other to provide an increased stroke and an increased region of reduced pressure in the cylinder member.
 11. A jarring stroke accelerator of the character set forth in claim 10 wherein: one of said plurality of members comprises a piston and a tubular stem movable in the cylinder member; sealing means is provided on said piston sealing between the piston and cylinder member; second sealing means is provided between said tubular stem and said cylinder member at one end of said cylinder member for sealing therebetween; a second piston and rod member is movable in the bore of said tubular stem with one end of said rod projecting from the bore of the stem, means sealing between said second piston and said tubular stem; and means for sealing between said rod and said tubular stem at the end of said stem opposite the piston thereon.
 12. A jarring stroke accelerator of the character set forth in claim 1 wherein said rod comprises a tubular stem having a piston thereon; a stationary rod is disposed in the tubular stem and is secured to one end of the cylinder member and extends to the opposite end thereof and is disposed to telescope into and out of said tubular stem; sealing means is provided for sealing between said piston and said cylinder and second sealing means is provided for sealing between said piston and said stationary rod; and means is provided for removably closing the bore of said tubular stem at the end thereof opposite the piston thereon.
 13. A method of the character set forth in claim 7 including: the additional step of further moving the pumpdown well tool string by movement of the operating fluid in said installation after said jarring device has been actuated.
 14. A method of accelerating the jarring stroke of a jarring device connected in a string of pumpdown well tools having a pumpdown locomotive therein operable by movement of circulating pumpdown fluid in a U-tube pumpdown well installation which includes: positioning a jarring stroke accelerator in the pumpdown tool string adjacent the locomotive and the jarring device connected in said string; moving said string of tools into said well installation U-tube by circulating pumpdown fluid to move said locomotive; creating a region of reduced pressure in the accelerator by circulating pumpdown fluid in the system to actuate said accelerator to produce said region of reduced pressure; applying force to said jarring device by means of the pumpdown fluid to release the jarring device for actuation; actuating said jarring device by moving the locomotive by means of the operating fluid in a direction to collapse the region of reduced pressure in the accelerator to provide sudden jarring movement of the jarring device.
 15. A jarring stroke accelerator of the character set fortH in claim 1 wherein the sealing means provided sealing between the piston and the bore wall of the cylinder member comprises a one-way seal on said piston.
 16. A jarring stroke accelerator of the character set forth in claim 8 wherein the means in the inlet opening means of said cylinder member for closing the said opening means comprises a one-way check valve by preventing flow of fluids through the inlet opening means into the cylinder member bore. 